Primary Key:
A Primary Key in a
Example:
Students in Universities are assigned a unique registration number.
Therefore, in a STUDENT database table, the attribute “reg_no” acts as primary key.
Foreign Key:
Foreign Key is a column in a relational database table which provides a relation between two tables. It provides a cross reference between tables by pointing to primary key of another table.
Example:
In STUDENT database table, the attribute “reg_no” acts as primary key and in COURSE database table in which the student selects his or her course, the same “reg_no” acts as foreign key for the STUDENT table.
Many to One Relationship:
When more than one record in a database table is associated with only one record in another table, the relationship between the two tables is referred as many to one relationship. It is also represented as M: 1 relationship.
One to Many Relationship:
When one record in a database table is associated with more than one record in another table, the relationship between the two tables is referred as one to many relationship. It is also represented as1: M relationship. This is the opposite of many to one relationship.
RELATIONAL DIAGRAM:
Relational Diagram is also known as Entity Relational Diagram. It is used to define the conceptual view of the database as viewed by the end user. It is used to depict the database’s main components: entities, relationships and attributes. It describes how data is related to each other.
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Chapter 3 Solutions
Database Systems: Design, Implementation, Management, Loose-leaf Version
- Create the table that results from applying an INTERSECT relational operator to the tables shown in Figure Q3.13. FIGURE Q3.13 THE CH03_VENDINGCO DATABASE TABLESarrow_forwardFor each table, identify the primary key and the foreign key(s). If a table does not have a foreign key, write None. FIGURE P3.17 THE CH03_TRANSCO DATABASE TABLESarrow_forwardUse Figure Q3.13 to answer Questions 1317. FIGURE Q3.13 THE CH03_VENDINGCO DATABASE TABLES Write the relational algebra formula to apply a UNION relational operator to the tables shown in Figure Q3.13.arrow_forward
- Using the tables in Figure Q3.13, create the table that results from MACHINE DIFFERENCE BOOTH. FIGURE Q3.13 THE CH03_VENDINGCO DATABASE TABLESarrow_forwardAn EMPLOYEES table was added to the JustLee Books database to track employee information. Display a list of each employee’s name, job title, and manager’s name. Use column aliases to clearly identify employee and manager name values. Include all employees in the list and sort by manager name.arrow_forwardHow is the processing of SQL DDL statements (such as CREATE TABLE) different from the processing required by DML statements?arrow_forward
- Problem 1 and 2 are based on the following query: SELECT EMP_LNAME, EMP_FNAME, EMP_AREACODE, EMP_SEX FROM EMPLOYEE WHERE EMP_SEX = 'F' AND EMP_AREACODE = '615' ORDER BY EMP_LNAME, EMP_FNAME; What indexes should you create? Write the required SQL commands.arrow_forwardProblems 27 and 28 are based on the following query: SELECT P_CODE, P_DESCRIPT, P_QOH, P_PRICE, V_CODE FROM PRODUCT WHERE P_QOH P_MIN AND P_MIN = P_REORDER AND P_REORDER = 50 ORDER BY P_QOH; What indexes would you recommend? Write the commands to create those indexes.arrow_forwardProblems 2224 are based on the following query: SELECT P_CODE, P_DESCRIPT, P_PRICE, P.V_CODE, V_STATE FROM PRODUCT P, VENDOR V WHERE P.V_CODE = V.V_CODE AND V_STATE = 'NY' AND V_AREACODE = '212' ORDER BY P_PRICE; Write the commands required to create the indexes you recommended in Problem 22.arrow_forward
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